Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Wavelength Division Multiplexing (WDM) Passive Optical Network (PON) is a recently developed network technology for meeting the rapidly increasing traffic demands caused by the popularization of the Internet and spouting of bandwidth-demanding applications. The inherent high cost of multi-wavelength provision may hinder the deployment of WDM PON. As compared to Time Division Multiplexing (TDM) PON, WDM PON may be associated with additional capital expenditure in enabling remote nodes, transmitters, and receivers with multi-wavelength provision capability. The multi-wavelength provision is one parameter in determining the capacity of WDM PON architecture. Specifically, the capacity of a PON system may depend on the network architecture, wavelength supporting capability of optical devices, as well as data rate of the source generators and receivers.
Similar to multiple wavelength sources, tunable laser sources are able to generate multiple wavelengths one wavelength at a time. From a network operator's point of view, tunable lasers offer advantages such as simple inventory management, reduced sparing cost, and automated wavelength provisioning. From the MAC layer's point of view, in the case of wavelength-fixed lasers, one wavelength channel is utilized by a fixed set of lasers, and thus statistical multiplexing gain cannot be exploited for traffic from lasers using different wavelength channels. In the case of wavelength tunable lasers, the wavelength tunability of tunable lasers facilitates the statistical multiplexing of traffic from a larger set of lasers, thus potentially yielding better system performance. The present disclosure appreciates that there are several limitations with designing WDM PONs with tunable laser optical network units (ONUs). For example, laser tuning times range from a few tens of nanoseconds to seconds, or even minutes, depending on the adopted technology. Different laser tuning times may introduce different network performances. Thus, scheduling of network traffic on ONUs may become complex given different laser tuning times.